Hydroxysteroid dehydrogenases (HSDs) regulate the occupancy and activation of steroid hormone receptors by converting steroid hormones into their inactive metabolites. For a recent review, see Nobel et al., Eur. J. Biochem. 2001, 268:4113-4125.
There exist numerous classes of HSDs. The 11-beta-hydroxysteroid dehydrogenases (11 β-HSDs) catalyze the interconversion of active glucocorticoids (such as cortisol and corticosterone), and their inert forms (such as cortisone and 11-dehydrocorticosterone). The isoform 11-beta-hydroxysteroid dehydrogenase type 1 (11β-HSD1) is expressed in liver, adipose tissue, brain, lung and other glucocorticoid tissue and is a potential target for therapy directed at numerous disorders that may be ameliorated by reduction of glucocorticoid action, such as diabetes, obesity and age-related cognitive dysfunction. Seckl, et al., Endocrinology, 2001, 142:1371-1376.
The various isozymes of the 17-beta-hydroxysteroid dehydrogenases (17β-HSDs) bind to androgen receptors or estrogen receptors and catalyze the interconversion of various sex hormones including estradiol/estrone and testosterone/androstenedione. To date, six isozymes have been identified in humans and are expressed in various human tissues including endometrial tissue, breast tissue, colon tissue, and in the testes. 17-beta-Hydroxysteroid dehydrogenase type 2 (17β-HSD2) is expressed in human endometrium and its activity has been reported to be linked to cervical cancer. Kitawaki et al., J. Clin. Endocrin. Metab., 2000, 85:1371-3292-3296. 17-beta-Hydroxysteroid dehydrogenase type 3 (17β-HSD3) is expressed in the testes and its modulation may be useful for the treatment of androgen-related disorders.
Androgens and estrogens are active in their 17β-hydroxy configurations, whereas their 17-keto derivatives do not bind to androgen and estrogen receptors and are thus inactive. The conversion between the active and inactive forms (estradiol/estrone and testosterone/androstenedione) of sex hormones is catalyzed by members of the 17β-HSD family. 17β-HSD1 catalyzes the formation of estradiol in breast tissue, which is important for the growth of malignant breast tumors. Labrie et al., Mol. Cell. Endocrinol. 1991, 78:C113-C118. A similar role has been suggested for 17β-HSD4 in colon cancer. English et al., J. Clin. Endocrinol. Metab. 1999, 84:2080-2085. 17β-HSD3 is almost exclusively expressed in the testes and converts androstenedione into testosterone. Deficiency of this enzyme during fetal development leads to male pseudohermaphroditism. Geissler et al., Nat. Genet. 1994, 7:34-39. Both 17β-HSD3 and various 3α-HSD isozymes are involved in complex metabolic pathways which lead to androgen shuffles between inactive and active forms. Penning et al., Biochem. J. 2000, 351:67-77. Thus, modulation of certain HSDs can have potentially beneficial effects in the treatment of androgen- and estrogen-related disorders.
The 20-alpha-hydroxysteroid dehydrogenases (20α-HSDs) catalyze the interconversion of progestins (such as between progesterone and 20α-hydroxy progesterone). Other substrates for 20α-HSDs include 17α-hydroxypregnenolone or 17α-hydroxyprogesterone, leading to 20α-OH steroids. Several 20α-HSD isoforms have been identified and 20α-HSDs are expressed in various tissues, including the placenta, ovaries, testes and adrenals. Peltoketo, et al., J. Mol. Endocrinol. 1999, 23:1-11.
The 3-alpha-hydroxysteroid dehydrogenases (3α-HSDs) catalyze the interconversion of the androgens dihydrotestosterone (DHT) and 5α-androstane-3α,17β-diol and the interconversion of the androgens DHEA and androstenedione and therefore play an important role in androgen metabolism. Ge et al., Biology of Reproduction 1999, 60:855-860.
Glucorticoids, Diabetes and Hepatic Glucose Production
It has been known for more than half a century that glucocorticoids have a central role in diabetes. For example, the removal of the pituitary gland or the adrenal gland from a diabetic animal alleviates the most severe symptoms of diabetes and lowers the concentration of glucose in the blood (Long, C. D. and Leukins, F. D. W. (1936) J. Exp. Med. 63: 465-490; Houssay, B. A. (1942) Endocrinology 30: 884-892). It is also well established that glucocorticoids enable the effect of glucagon on the liver.
The role of 11βHSD1 as an important regulator of local glucocorticoid effect and thus of hepatic glucose production is well substantiated (see, e.g., Jamieson et al. (2000) J. Endocrinol. 165: 685-692). Hepatic insulin sensitivity was improved in healthy human volunteers treated with the non-specific 11βHSD1 inhibitor carbenoxolone (Walker, B. R. et al. (1995) J. Clin. Endocrinol. Metab. 80: 3155-3159). Furthermore, the expected mechanism has been established by different experiments with mice and rats. These studies showed that the mRNA levels and activities of two key enzymes in hepatic glucose production were reduced, namely: the rate-limiting enzyme in gluconeogenesis, phosphoenolpyruvate carboxykinase (PEPCK), and glucose-6-phosphatase (G6 Pase) the enzyme catalyzing the last common step of gluconeogenesis and glycogenolysis. Finally, blood glucose levels and hepatic glucose production are reduced in mice in which the 11βHSD1 gene is knocked-out. Data from this model also confirm that inhibition of 11βHSD1 will not cause hypoglycemia, as predicted since the basal levels of PEPCK and G6 Pase are regulated independently of glucocorticoids (Kotelevtsev, Y. et al., (1997) Proc. Natl. Acad. Sci. USA 94: 14924-14929).
FR 2,384,498 discloses compounds having a high hypoglycemic effect. Therefore, treatment of hyperglycemia with these compounds may lead to hypoglycemia.
Reduction of Obesity and Obesity Related Cardiovascular Risk Factors
Obesity is an important factor in syndrome X as well as in the majority (>80%) of type 2 diabetes, and omental fat appears to be of central importance. Abdominal obesity is closely associated with glucose intolerance, hyperinsulinemia, hypertriglyceridemia, and other factors of the so-called syndrome X (e.g. increased blood pressure, decreased levels of HDL and increased levels of VLDL) (Montague & O'Rahilly, Diabetes 49: 883-888, 2000). Inhibition of the 11βHSD1 enzyme in pre-adipocytes (stromal cells) has been shown to decrease the rate of differentiation into adipocytes. This is predicted to result in diminished expansion (possibly reduction) of the omental fat depot, i.e., reduced central obesity (Bujalska, I. J., S. Kumar, and P. M. Stewart (1997) Lancet 349: 1210-1213).
Inhibition of 11βHSD1 in mature adipocytes is expected to attenuate secretion of the plasminogen activator inhibitor 1 (PAI-1)—an independent cardiovascular risk factor (Halleux, C. M. et al. (1999) J. Clin. Endocrinol. Metab. 84: 4097-4105). Furthermore, there is a clear correlation between glucocorticoid “activity” and cardiovascular risk factor suggesting that a reduction of the glucocorticoid effects would be beneficial (Walker, B. R. et al. (1998) Hypertension 31: 891-895; Fraser, R. et al. (1999) Hypertension 33: 1364-1368).
Adrenalectomy attenuates the effect of fasting to increase both food intake and hypothalamic neuropeptide Y expression. This supports the role of glucocorticoids in promoting food intake and suggests that inhibition of 11βHSD1 in the brain might increase satiety and therefore reduce food intake (Woods, S. C. et al. (1998) Science, 280: 1378-1383).
Beneficial Effect on the Pancreas
Inhibition of 11βHSD1 in isolated murine pancreatic β-cells improves glucose-stimulated insulin secretion (Davani, B. et al. (2000) J. Biol. Chem. 2000 Nov. 10; 275(45): 34841-4). Glucocorticoids were previously known to reduce pancreatic insulin release in vivo (Billaudel, B. and B. C. J. Sutter (1979) Horm. Metab. Res. 11: 555-560). Thus, inhibition of 11βHSD1 is predicted to yield other beneficial effects for diabetes treatment, besides the effects on liver and fat.
Beneficial Effects on Cognition and Dementia
Stress and glucocorticoids influence cognitive function (de Quervain, D. J.-F., B. Roozendaal, and J. L. McGaugh (1998) Nature 394: 787-790). The enzyme 11βHSD1 controls the level of glucocorticoid action in the brain and thus contributes to neurotoxicity (Rajan, V., C. R. W. Edwards, and J. R. Seckl, J. (1996) Neuroscience 16: 65-70; Seckl, J. R., Front. (2000) Neuroendocrinol. 18: 49-99). Unpublished results indicate significant memory improvement in rats treated with a non-specific 11βHSD1 inhibitor (J. Seckl, personal communication). Based the above and on the known effects of glucocorticoids in the brain, it may also be suggested that inhibiting 11βHSD1 in the brain may result in reduced anxiety (Tronche, F. et al. (1999) Nature Genetics 23: 99-103). Thus, taken together, the hypothesis is that inhibition of 11βHSD1 in the human brain would prevent reactivation of cortisone into cortisol and protect against deleterious glucocorticoid-mediated effects on neuronal survival and other aspects of neuronal function, including cognitive impairment, depression, and increased appetite.
Use of Immuno-Modulation Using 11βHSD1 Inhibitors
The general perception is that glucocorticoids suppress the immune system. But in fact there is a dynamic interaction between the immune system and the HPA (hypothalamo-pituitary-adrenal) axis (Rook, G. A. W. (1999) Baillièr's Clin. Endocrinol. Metab. 13: 576-581). The balance between the cell-mediated response and humoral responses is modulated by glucocorticoids. A high glucocorticoid activity, such as at a state of stress, is associated with a humoral response. Thus, inhibition of the enzyme 11βHSD1 has been suggested as a means of shifting the response towards a cell-based reaction.
In certain disease states, including tuberculosis, lepra and psoriasis the immune reaction is normally biased towards a humoral response when in fact the appropriate response would be cell based. Temporal inhibition of 11βHSD1, local or systemic, might be used to push the immune system into the appropriate response (Mason, D. (1991) Immunology Today 12: 57-60; Rook et al., supra).
An analogous use of 11βHSD1 inhibition, in this case temporal, would be to booster the immune response in association with immunization to ensure that a cell based response would be obtained, when desired.
Reduction of Intraocular Pressure
Recent data suggest that the levels of the glucocorticoid target receptors and the 11βHSD enzymes determines the susceptibility to glaucoma (Stokes, J. et al. (2000) Invest. Opthalmol. 41: 1629-1638). Further, inhibition of 11βHSD1 was recently presented as a novel approach to lower the intraocular pressure (Walker E. A. et al, poster P3-698 at the Endocrine society meeting Jun. 12-15, 1999, San Diego). Ingestion of carbenoxolone, a non-specific inhibitor of 11βHSD1, was shown to reduce the intraocular pressure by 20% in normal subjects. In the eye, expression of 11βHSD1 is confined to basal cells of the corneal epithelium and the non-pigmented epithelialium of the cornea (the site of aqueous production), to ciliary muscle and to the sphincter and dilator muscles of the iris. In contrast, the distant isoenzyme 11βHSD2 is highly expressed in the non-pigmented ciliary epithelium and corneal endothelium. None of the enzymes is found at the trabecular meshwork, the site of drainage. Thus, 11βHSD1 is suggested to have a role in aqueous production, rather than drainage, but it is presently unknown if this is by interfering with activation of the glucocorticoid or the mineralocorticoid receptor, or both.
Reduced Osteoporosis
Glucocorticoids have an essential role in skeletal development and function but are detrimental in excess. Glucocorticoid-induced bone loss is derived, at least in part, via inhibition of bone formation, which includes suppression of osteoblast proliferation and collagen synthesis (Kim, C. H., Cheng, S. L. and Kim, G. S. (1999) J. Endocrinol. 162: 371-379). The negative effect on bone nodule formation could be blocked by the non-specific inhibitor carbenoxolone suggesting an important role of 11βHSD1 in the glucocorticoid effect (Bellows, C. G., Ciaccia, A. and Heersche, J. N. M. (1998) Bone 23: 119-125). Other data suggest a role of 11βHSD1 in providing sufficiently high levels of active glucocorticoid in osteoclasts, and thus in augmenting bone resorption (Cooper, M. S. et al. (2000) Bone 27: 375-381). Taken together, these different data suggest that inhibition of 11βHSD1 may have beneficial effects against osteoporosis by more than one mechanism working in parallel.
Reduction of Hypertension
Bile acids inhibit 11β-hydroxysteroid dehydrogenase type 2. This results in a shift in the overall body balance in favour of cortisol over cortisone, as shown by studying the ratio of the urinary metabolites (Quattropani, C., Vogt, B., Odermatt, A., Dick, B., Frey, B. M., Frey, F. J. (2001) J Clin Invest. November; 108(9):1299-305. “Reduced activity of 11beta-hydroxysteroid dehydrogenase in patients with cholestasis”.). Reducing the activity of 11β-HSD1 in the liver by a selective inhibitor is predicted to reverse this imbalance, and acutely counter the symptoms such as hypertension, while awaiting surgical treatment removing the biliary obstruction.
Wound Healing
Cortisol performs a broad range of metabolic functions and other functions. The multitude of glucocorticoid action is exemplified in patients with prolonged increase in plasma glucocorticoids, so called “Cushing's syndrome”. Patients with Cushing's syndrome have prolonged increase in plasma glucocorticoids and exhibit impaired glucose tolerance, type 2 diabetes, central obesity, and osteoporosis. These patients also have impaired wound healing and brittle skin (Ganong, W. F. Review of Medical Physiology. Eighteenth edition ed. Stamford, Conn.: Appleton & Lange; 1997).
Glucocorticoids have been shown to increase risk of infection and delay healing of open wounds (Anstead, G. M. Steroids, retinoids, and wound healing. Adv Wound Care 1998; 11(6):277-85). Patients treated with glucocorticoids have 2-5-fold increased risk of complications when undergoing surgery (Diethelm, A. G. Surgical management of complications of steroid therapy. Ann Surg 1977; 185(3):251-63).
The European patent application No. EP 0902288 discloses a method for diagnosing the status of wound healing in a patient, comprising detecting cortisol levels in said wound. The authors suggest that elevated levels of cortisol in wound fluid, relative to normal plasma levels in healthy individuals, correlates with large, non-healing wounds (Hutchinson, T. C., Swaniker, H. P., Wound diagnosis by quantitating cortisol in wound fluids. European patent application No. EP 0 902 288, published Mar. 17, 1999).
In humans, the 11β-HSD catalyzes the conversion of cortisol to cortisone, and vice versa. The parallel function of 11β-HSD in rodents is the interconversion of corticosterone and 11-dehydrocorticosterone (Frey, F. J., Escher, G., Frey, B. M. Pharmacology of 11 beta-hydroxysteroid dehydrogenase. Steroids 1994; 59(2):74-9). Two isoenzymes of 11β-HSD, 11β-HSD1 and 11β-HSD2, have been characterized, and differ from each other in function and tissue distribution (Albiston, A. L., Obeyesekere, V. R., Smith, R. E., Krozowski, Z. S. Cloning and tissue distribution of the human 11 beta-hydroxysteroid dehydrogenase type 2 enzyme. Mol Cell Endocrinol 1994; 105(2):R11-7). Like GR, 11β-HSD1 is expressed in numerous tissues like liver, adipose tissue, adrenal cortex, gonads, lung, pituitary, brain, eye etc (Monder C, White P C. 11 beta-hydroxysteroid dehydrogenase. Vitam Horm 1993; 47:187-271; Stewart, P. M., Krozowski, Z. S. 11 beta-Hydroxysteroid dehydrogenase. Vitam Horm 1999; 57:249-324; Stokes, J., Noble, J., Brett, L., Phillips, C., Seckl, J. R., O'Brien, C., et al. Distribution of glucocorticoid and mineralocorticoid receptors and 11beta-hydroxysteroid dehydrogenases in human and rat ocular tissues. Invest Opthalmol Vis Sci 2000; 41(7):1629-38). The function of 11β-HSD1 is to fine-tune local glucocorticoid action. 11β-HSD activity has been shown in the skin of humans and rodents, in human fibroblasts and in rat skin pouch tissue (Hammami, M. M., Siiteri, P. K. Regulation of 11 beta-hydroxysteroid dehydrogenase activity in human skin fibroblasts: enzymatic modulation of glucocorticoid action. J Clin Endocrinol Metab 1991; 73(2):326-34); Cooper, M. S., Moore, J., Filer, A., Buckley, C. D., Hewison, M., Stewart, P. M. 11beta-hydroxysteroid dehydrogenase in human fibroblasts: expression and regulation depends on tissue of origin. ENDO 2003 Abstracts 2003; Teelucksingh, S., Mackie, A. D., Burt, D., McIntyre, M. A., Brett, L., Edwards, C. R. Potentiation of hydrocortisone activity in skin by glycyrrhetinic acid. Lancet 1990; 335(8697): 1060-3; Slight, S. H., Chilakamarri, V. K., Nasr, S., Dhalla, A. K., Ramires, F. J., Sun, Y., et al. Inhibition of tissue repair by spironolactone: role of mineralocorticoids in fibrous tissue formation. Mol Cell Biochem 1998; 189(1-2):47-54).
Wound healing consists of serial events including inflammation, fibroblast proliferation, secretion of ground substances, collagen production, angiogenesis, wound contraction and epithelialization. It can be divided in three phases; inflammatory, proliferative and remodeling phase (reviewed in Anstead et al., supra).
In surgical patients, treatment with glucocorticoids increases risk of wound infection and delay healing of open wounds. It has been shown in animal models that restraint stress slows down cutaneous wound healing and increases susceptibility to bacterial infection during wound healing. These effects were reversed by treatment with the glucocorticoid receptor antagonist RU486 (Mercado, A. M., Quan, N., Padgett, D. A., Sheridan, J. F., Marucha, P. T. Restraint stress alters the expression of interleukin-1 and keratinocyte growth factor at the wound site: an in situ hybridization study. J Neuroimmunol 2002; 129(1-2):74-83; Rojas, I. G., Padgett, D. A., Sheridan, J. F., Marucha, P. T. Stress-induced susceptibility to bacterial infection during cutaneous wound healing. Brain Behav Immun 2002; 16(1):74-84). Glucocorticoids produce these effects by suppressing inflammation, decrease wound strength, inhibit wound contracture and delay epithelialization (Anstead et al., supra). Glucocorticoids influence wound healing by interfering with production or action of cytokines and growth factors like IGF, TGF-β, EGF, KGF and PDGF (Beer, H. D., Fassler, R., Werner, S. Glucocorticoid-regulated gene expression during cutaneous wound repair. Vitam Horm 2000; 59:217-39; Hamon, G. A., Hunt, T. K., Spencer, E. M. In vivo effects of systemic insulin-like growth factor-I alone and complexed with insulin-like growth factor binding protein-3 on corticosteroid suppressed wounds. Growth Regul 1993; 3(1):53-6; Laato, M., Heino, J., Kahari, V. M., Niinikoski, J., Gerdin, B. Epidermal growth factor (EGF) prevents methylprednisolone-induced inhibition of wound healing. J Surg Res 1989; 47(4):354-9; Pierce, G. F., Mustoe, T. A., Lingelbach, J., Masakowski, V. R., Gramates, P., Deuel, T. F. Transforming growth factor beta reverses the glucocorticoid-induced wound-healing deficit in rats: possible regulation in macrophages by platelet-derived growth factor. Proc Natl Acad Sci USA 1989; 86(7):2229-33). It has also been shown that glucocorticoids decrease collagen synthesis in rat and mouse skin in vivo and in rat and human fibroblasts (Oishi, Y., Fu, Z. W., Ohnuki, Y., Kato, H., Noguchi, T. Molecular basis of the alteration in skin collagen metabolism in response to in vivo dexamethasone treatment: effects on the synthesis of collagen type I and III, collagenase, and tissue inhibitors of metalloproteinases. Br J Dermatol 2002; 147(5):859-68).
EP 0 558 258, EP 0 569 193, and EP 1 069 114 disclose isoxazole derivatives as endothelin agonists and antagonists. These publications do not address the activity of the compounds on 11β-HSD1.